Piezoelectric components can be embodied as multilayer components from a stack of alternatingly arranged piezoelectric ceramic layers and electrode layers and are becoming ever more important in modern electrical engineering. For example piezoelectric components in the form of piezo actors are used as control drives in conjunction with valves and similar devices.
A known piezo actor is for example described in DE 196 46 676 C1. These types of piezo ceramics utilize the effect in which they are charged up under a mechanical pressure or tension and on the other hand expand when an electrical voltage is applied along the main axis of the ceramic layer. To multiply the usable length extension monolithic multilayer actors are used for example which consist of a sintered stack of thin foils of piezo ceramic (for example lead zirconium titanate) with interleaved metallic electrode layers. The electrode layers are brought out of the stack alternately and connected piezoelectrically in parallel via external metalization. For this purpose, through metalization in the form of a strip or band is applied to the two contact sides of the stack which is connected to all electrode layers of the same polarity. Additional contacting which is still executed in many forms is still frequently applied between the metalization and the electrical access elements of the piezoelectric component. If an electrical voltage is applied to the electrical access elements, the piezo foils expand in the field direction. By mechanical series connection of the individual piezo foils the nominal expansion of the entire stack is already reached at relatively low electrical voltages.
These types of actors are subjected to a considerable stress by the mechanical lifting. Of decisive significance for the lifetime of these types of actors in dynamic operation, to achieve higher numbers of cycles and higher reliability, is electrical external contacting. Current deigns of multilayer actors contain up to several hundred electrode layers which are generated for example by screen printing of a silver palladium paste and subsequent co-firing with the ceramic layers. These electrode layers must be connected reliably and permanently with the external electrical connection elements. Since continuity metalization can also be interrupted in dynamic operation at individual points, for example by tears or similar occurring, additional contacting or the connection of the metalization with the outgoing electrical connection elements must be made via a larger number of parallel connection elements, which can take the form of thin conductor tracks, wires or such like.
Such additional contacting is for example also disclosed in the older Patent Application DE 198 18 068 also submitted by the applicant. In this the electrode layers of one polarity of a piezoelectric actor are initially connected to each other via continuity metalization. To connect the metalization to electrical connections a series of connecting elements are provided.